A transformer is a magnetic device that transfers electric energy from one circuit to another circuit through coils in order to regulate an input voltage to a desired range for powering an electronic device. Conventionally, the transformer includes a bobbin, a magnetic core assembly, a primary winding coil, and a secondary winding coil. The primary winding coil and the secondary winding coil are wound around a winding section of the bobbin. During operations of the transformer, an input voltage is inputted into the primary winding coil, the magnetic core assembly is subject to electromagnetic induction, and a regulated voltage is outputted from the secondary winding coil.
FIG. 1A is a schematic exploded view illustrating a conventional transformer. FIG. 1B is a schematic perspective view illustrating the assembled structure of the transformer of FIG. 1A. As shown in FIGS. 1A and 1B, the conventional transformer 1 includes an insulation case 10, a bobbin 11, a magnetic core assembly 12, a primary winding coil (not shown), and a secondary winding coil 13. A positioning structure 101 is protruded from a sidewall of the insulation case 10. In addition, the positioning structure 101 has positioning holes 102. A process of assembling the conventional transformer 1 will be illustrated as follows. Firstly, the primary winding coil and the secondary winding coil 13 are wound on a winding section (not shown) of the bobbin 11. In addition, the outlet parts 131 of the secondary winding coil 13 are outputted from a lateral side of the bobbin 13. After the primary winding coil and the secondary winding coil 13 are wound on the bobbin 11, the bobbin 11 and the magnetic core assembly 12 are combined together. Then, the combination of the bobbin 11 and the magnetic core assembly 12 is placed in an accommodation space 100 of the insulation case 10. In addition, the outlet parts 131 of the secondary winding coil 13 are positioned in the corresponding positioning holes 102 of the insulation case 10. The resulting structure of the assembled transformer 1 is shown in FIG. 1B. For separating the primary winding coil from the secondary winding coil 13 and meeting the safety requirements, the transformer 1 is additionally equipped with the insulation case 10. As known, the arrangement of the insulation case 10 may increase isolation and creepage distance of the transformer 1 in order to enhance the electrical safety. However, the use of the insulation case 10 may increase the fabricating cost of the transformer 1 and increase the overall volume of the transformer 1.
FIG. 2 is a schematic perspective view illustrating another conventional transformer. As shown in FIG. 2, the transformer 2 includes a bobbin 21, a magnetic core assembly 22, a primary winding coil (not shown), and a secondary winding coil 23. In addition, the transformer 2 further includes an insulation tape 20. The function of the insulation tape 20 is similar to the function of the insulation case 10 of FIG. 1. The bobbin 21 further includes a base 211. The base 211 is extended from the bobbin 21 along an extending direction of the outlet parts 231 of the secondary winding coil 23. Moreover, the base 211 includes a positioning structure 212 for positioning the outlet parts 231 of the secondary winding coil 23. Moreover, the insulation tape 20 is wound around the bobbin 21, the magnetic core assembly 22, the primary winding coil and the secondary winding coil 23. Similarly, the insulation tape 20 may increase isolation of the transformer 2 in order to enhance the electrical safety. Since the insulation case is replaced by the insulation tape 20, the fabricating cost and the overall volume of the transformer 2 are reduced when compared with the transformer 1. However, since the base 211 with the positioning structure 212 are protruded from the bobbin 21, the length and height of the transformer 2 are still large. Under this circumstance, the applications of installing the transformer 2 on a circuit board (not shown) will be restricted.
Recently, the general trends in designing electronic device are toward small size, miniaturization and slimness. Correspondingly, the volume of the transformer for use in the electronic device should be reduced. In other words, the manufactures of transformers make efforts in reducing the thicknesses of the transformers. Moreover, for facilitating assemblage, the structure of the transformer should be as simple as possible. As previously described in FIG. 1, the transformer 1 uses the insulation case 10 for isolating the primary winding coil, the secondary winding coil 13 and the external electronic components from each other and positioning the outlet parts 131 of the secondary winding coil 13. The insulation case 10 may increase the length, width and height of the transformer 1. As previously described in FIG. 2, the insulation case is replaced by the insulation tape 20, and the base 211 is extended from the bobbin 21. However, the length and height of the transformer 2 are still large. In other words, the conventional transformers fail to meet the requirement of miniaturization and slimness.
Therefore, there is a need of providing an improved transformer in order to avoid the above drawbacks.